Abstract Vehicle collisions, flames and high-temperature smoke inside tunnels will generate factors for thermal ra? diation and thermal convection that can easily lead to dual-source or multi-source fire accidents, posing serious threats to the safety of people in the tunnel. To investigate the development characteristics of dual-source fires in tunnels under the condition of longitudinal ventilation, an on-site full-scale fire test is carried out based on the Beiheng Passageway in central urban Shanghai, which includes a total of five sets of fire tests using two sets of diesel pool fires. By changing the ignition time and spacing of the dual fire sources, it is focused on analyzing the characteristics of key parameters in the whole development process of chain-type dual-source fires and parallel-type dualsource fires with different source spacings, including flame deflection angle, heat release rate, vertical and longitudinal smoke temperature, and carbon monoxide concentration. The results show that due to different ignition time, the chain-type fires are not synchronized in development for the dual sources, and the heat release rate of the dualsource fires shows the development pattern of one growing and the other decaying, indicating a significant competi? tive combustion mechanism. For chain-type dual-source fires with a source spacing of 2 m, the flame deflection angle of the downstream fire source remains greater than that of the upstream fire source during different phases of development. For parallel-type dual-source fires with a source spacing of 5 m, 10 m and 20 m, the flame deflection angles of the duel-source fires are more or less consistent. In contrast to crown smoke temperature measurement schemes in extant full-scale tunnel fire tests, this study adopts Fiber Bragg Grating temperature sensors with a spacing of 1 m to measure the smoke temperature at the tunnel crown. For dual-source fires with different source spacings, there are multiple temperature peaks in the longitudinal distribution curve of smoke temperature on the crown.Whether the temperature peak is caused by thermal radiation or thermal convection, the temperature peak corresponding to the downstream fire source stays greater than that corresponding to the upstream fire source. As the source spacing increases, the maximum smoke temperature at the crown corresponding to the dual-source fire will gradually decrease. The distribution characteristics of smoke temperature at the downstream crown for both dualsource and single-source fires satisfy the exponential decay law.
Abstract：
Vehicle collisions, flames and high-temperature smoke inside tunnels will generate factors for thermal ra? diation and thermal convection that can easily lead to dual-source or multi-source fire accidents, posing serious threats to the safety of people in the tunnel. To investigate the development characteristics of dual-source fires in tunnels under the condition of longitudinal ventilation, an on-site full-scale fire test is carried out based on the Beiheng Passageway in central urban Shanghai, which includes a total of five sets of fire tests using two sets of diesel pool fires. By changing the ignition time and spacing of the dual fire sources, it is focused on analyzing the characteristics of key parameters in the whole development process of chain-type dual-source fires and parallel-type dualsource fires with different source spacings, including flame deflection angle, heat release rate, vertical and longitudinal smoke temperature, and carbon monoxide concentration. The results show that due to different ignition time, the chain-type fires are not synchronized in development for the dual sources, and the heat release rate of the dualsource fires shows the development pattern of one growing and the other decaying, indicating a significant competi? tive combustion mechanism. For chain-type dual-source fires with a source spacing of 2 m, the flame deflection angle of the downstream fire source remains greater than that of the upstream fire source during different phases of development. For parallel-type dual-source fires with a source spacing of 5 m, 10 m and 20 m, the flame deflection angles of the duel-source fires are more or less consistent. In contrast to crown smoke temperature measurement schemes in extant full-scale tunnel fire tests, this study adopts Fiber Bragg Grating temperature sensors with a spacing of 1 m to measure the smoke temperature at the tunnel crown. For dual-source fires with different source spacings, there are multiple temperature peaks in the longitudinal distribution curve of smoke temperature on the crown.Whether the temperature peak is caused by thermal radiation or thermal convection, the temperature peak corresponding to the downstream fire source stays greater than that corresponding to the upstream fire source. As the source spacing increases, the maximum smoke temperature at the crown corresponding to the dual-source fire will gradually decrease. The distribution characteristics of smoke temperature at the downstream crown for both dualsource and single-source fires satisfy the exponential decay law.
GUO Chao1,
2 YAN Zhiguo1,
2 LI Wei1 etc
.A Full-scale Experimental Study on the Fire Characteristics of Dual-source Tunnel Fire[J] MODERN TUNNELLING TECHNOLOGY, 2023,V60(2): 247-259
2023, Vol. 60 